In clean rooms used heretofore, for example, in factories or research laboratories in the relevant field of semiconductors, foodstuffs, medicines and biotechnology, dry air filters for trapping air-born particles are disposed to air introduction paths and air passing therethrough is introduced into the clean room.
Air filters used at present in clean rooms include ULPA (abbreviation for Ultra Low Penetration Air) using glass fibers for the filter medium and HEPA (abbreviation for High Efficiency Particle Air), and such filters are excellent filters in view of removal of dusts and, for example, ULPA filters can remove fine particles even of 0.1 .mu.m. Further, non-glass type filters using fluoro resin or quartz fibers instead of the glass fibers for the filter medium have also been developed so as not to release inorganic substances from the air filters.
Recently, with the increase of integration degree of semiconductors, diffusing of gaseous organic substances as well as dusts in the clean room air have considered to be the cause of the defects. That is, it has been pointed out that organic substances are adsorbed on the surface of semiconductor substrates (silicon wafers) in clean rooms, to deteriorate device characteristics (for example, Fujii, "Gaseous Contaminants and Current Situation for Countermeasure of Removal", Air Cleaning, Vol. 32, No. 3, p 43 (1994), published from the Foundation of Japan Air Cleaning Society).
Further, it has been well-known that an n-type semiconductor is obtained by doping P (phosphorus) and a p-type semiconductor is obtained by doping B (boron) into a silicon wafer in semiconductor manufacturing steps but, if phosphorus compounds or boron compounds are present in the clean room air, these may possibly cause unnecessary doping, so that it is necessary to remove such ingredients from the clean room air.
The present invention has been accomplished to solve the problems described above and it is an object thereof to provide an air filter for trapping air-born particles that can eliminate the presence of gaseous organic substances, for example, in clean rooms, semiconductor production apparatus or the like, a method of manufacturing an air filter therefor, a treatment agent constituting the air filter, a method of manufacturing a filter medium, a clean room and a local facility such as a semiconductor production apparatus in which gaseous organic substances are not present, as well as a clean room and a local facility in which phosphorus compounds and boron compounds are not present.